Basin Compartmentalization in the Foreland: El Cajon Basin, Southwestern Argentina

Shell Oil Corp

Cenozoic tectonic and geomorphic evolution of the Red River Region, Yunnan Province, China

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2004.Some pages folded.Includes bibliographical references.(cont.) Xianshuihe-Xiaojiang fault system during growth of the southeast plateau margin. Cosmogenic ²⁶A1 and ¹⁰Be basin-wide erosion rate and burial ages indicate a background incision rate of [approximately] 0.05 to 0.10 mm/a, lower than the long-term incision rate minimum of [approximately] 0.26 mm/a. Cosmogenically-determined incision rate approximately doubles to [approximately] 0.20 mm/a in the region of maximum dip-slip displacement on the Red River fault. This thesis also develops a new cosmogenic tool for quantitative landscape analysis: using depth dependence data for multiple cosmogenic nuclides from a single site to constrain an erosion history. This method is applied in the Dry Valleys region of Antarctica.This thesis outlines the Cenozoic development of the Red River region, exploring regional landscape evolution and tectonic accommodation of the India-Eurasia collision, focusing on the Oligo-Miocene, left-lateral Ailao Shan shear zone and the active, right-lateral Red River fault on the northeast margin of the shear zone, along which the Red River has incised a deep valley. Oligo-Miocene fluvial and alluvial conglomerates in the valley record shear zone unroofing: pervasive, syn-depositional shortening indicates transpressional exhumation. A low-relief landscape, developed in Late Miocene time, was probably uplifted in Pliocene time, triggering the incision of the Red River and isolating the low-relief landscape from modem base level. On the basis of stratigraphic data, river incision began in Pliocene time or later. Tributary longitudinal profiles indicate two-phase incision, the result of pulsed plateau growth or trunk channel adjustments to changing climate conditions. Paleo-Red River reconstruction indicates [approximately] 1400 m river incision, 1400-1500 m surface uplift and 750 m vertical displacement across the northern part of the Red River fault. Minimum right-lateral displacement on the fault is 40 km, 15-16 km of which predates river incision, plateau growth and development of other regional fault systems. Long term average slip-rate is a minimum of [approximately] 5 mm/yr. Rotation of a crustal fragment around the eastern Himalayan syntaxis, bounded on the east by the Xianshuihe-Xiaojiang fault system, causes deflection of the Red River fault, accommodated by distributed shear along strike of the Xianshuihe-Xiaojiang fault system. The Red River fault has decreased in regional importance since the initiation of theby Lindsay M. Schoenbohm.Ph.D

Late Cenozoic tectonic evolution of the Ailao Shan-Red River fault (SE Tibet): implications for kinematic change during plateau growth

Surface uplift, river incision, shear zone exhumation, and displacement along active faults have all interacted to shape the modern landscape in the southeastern margin of the Tibetan Plateau. The Ailao Shan-Red River fault, a major structure in the tectonic evolution of southeastern Asia, is an excellent recorder of these processes. We present new stratigraphic, structural, and low-temperature thermochronologic data to explore its late Cenozoic tectonic and geomorphic evolution. The stratigraphic and structural observations indicate that the major bend in the fault was a releasing bend with significant Miocene sedimentation in the early–middle Miocene but became a restraining bend with abundant shortening structures developed after the late Miocene reversal of displacement. We also document exhumation of the shear zone from two low-temperature thermochronologic transects. New apatite (U-Th)/He(AHe) data and published thermochronologic results reveal two accelerated cooling episodes, backed by stratigraphic and geomorphic observations. The first rapid cooling phase occurred from ca. 27 to 17 Ma with removal of cover rocks and exhumation of the shear zone. The second accelerated cooling episode revealed by our AHe data commenced at 14–13 Ma, lasting 2–3 Myr. The Ailao Shan range may have risen to its modern elevation with high-relief topography developing due to river incision. We interpret the onset of this rapid exhumation to reflect renewed plateau growth associated with lower crustal flow

Recent, slow normal and strike-slip faulting in the Pasto Ventura region of the southern Puna Plateau, NW Argentina

Recent normal and strike-slip faulting on the Puna Plateau of NW Argentina has been linked to lithospheric foundering, gravitational spreading, plate boundary forces and a decrease in crustal shortening from north to south. However, the timing, kinematics and rate of extension remain poorly constrained. We focus on the Pasto Ventura region (NW Argentina) located on the southern Puna Plateau and recent deformation

Late Quaternary Activity of the La Rinconada Fault Zone, San Juan, Argentina

Most of the permanent deformation in the Pampean Flat slab segment of the central Andes is taken up at the Andean Orogenic Front in Argentina, a narrow zone between the Eastern Precordillera and Sierras Pampeanas that comprises one of the world's most seismically active thrust zones. Active faults and folds in the region have been extensively mapped but still largely lack information on style and rates of deformation, which is essential for understanding the distribution of regional strain and estimating the seismic potential of individual faults. Structural, geomorphic, and 36Cl cosmogenic radionuclide surface exposure age methods are used to focus on key sites along the 30-km-long La Rinconada Fault Zone in this region of west-central Argentina, which is ~15 km away from the highly populated (~500,000) city of San Juan, to define a late Quaternary average shortening rate of 0.41 ± 0.01 mm/year. This slip rate is the same order of magnitude, but slightly lower than nearby similar east dipping Eastern Precordillera faults including the La Laja and Las Tapias Faults. Relatively low slip rates are interpreted as being a consequence of distributed deformation between the latitude of the La Rinconada Fault Zone (31 and 32°S), as compared to between latitudes 32 to 33°S where deformation appears to be focused on fewer structures, including the Las Peñas and La Cal Thrust Faults. The La Rinconada Fault Zone is capable of generating earthquakes of Mw 6.6–7.2, but further investigations are required to determine timing and recurrence intervals of discrete events.Fil: Rimando, Jeremy. University of Toronto; CanadáFil: Schoenbohm, Lindsay. University of Toronto; CanadáFil: Costa, Carlos Horacio. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; ArgentinaFil: Owen, Lewis. University of Cincinnati; Estados UnidosFil: Cesta, Jason M.. University of Cincinnati; Estados UnidosFil: Richard, Andrés David. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; ArgentinaFil: Gardini, Carlos Enrique. Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis; Argentin

Late Quaternary intraplate deformation defined by the Las Chacras Fault Zone, West‐Central Argentina

Several major (up to MW 7.5) earthquakes over the past 320 years have shaken the thick-skinned Sierras Pampeanas region of Argentina, despite exhibiting much lower GPS-shortening rates than across the thin-skinned Precordillera region to its west. Whether geodetic shortening rates indicate an actual long-term shortening gradient, and whether shortening rates translate to higher uplift rates due to steeper faults in the Sierras Pampeanas, remain uncertain due to the limited spatio-temporal coverage and the inherently large error in the vertical component of deformation of GPS measurements. We measure geomorphic offsets and use 10Be terrestrial cosmogenic nuclide surface exposure dating to determine slip rates on the Las Chacras Fault Zone (LCFZ)—an ∼30 km long, NNW-trending, steeply dipping (55–65°E) reverse fault that branches off of the longest, westernmost, thick-skinned Valle Fértil range-front fault in the western Sierras Pampeanas. Average shortening and uplift rates measured on the LCFZ are ∼0.2 and ∼0.3–0.4 mm/yr, respectively. Despite an uplift rate similar to most other faults in the region, the LCFZ shortening rate is lower than faults to its west; this is in agreement with the inferred west-east decrease in shortening rates from GPS data, indicating consistent regional deformation patterns since the Late Pleistocene. The decrease in shortening to the east coincides spatially with the termination of the flat portion of the subducted Nazca plate between 67 and 68°W. From scaling relationships among magnitude, slip rate, and fault length, the LCFZ is capable of generating earthquakes of MW 6.7–7.1.Fil: Rimando, Jeremy. University of Toronto; CanadáFil: Schoenbohm, Lindsay. University of Toronto; CanadáFil: Ortiz, Gustavo Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; ArgentinaFil: Alvarado, Patricia Monica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; ArgentinaFil: Venerdini, Agostina Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geofísica y Astronomía; ArgentinaFil: Owen, Lewis. North Carolina State University; Estados UnidosFil: Seagren, Erin. University of Toronto; CanadáFil: Marques Figueiredo, Paula. North Carolina State University; Estados UnidosFil: Hammer, Sarah. University of Cincinnati; Estados Unido

Constraining Deformation in the North Pamir and the Westernmost Tarim Basin

Abstract HKT-ISTP 2013 A

Large-scale drainage capture and surface uplift in eastern Tibet–SW China before 24 Ma inferred from sediments of the Hanoi Basin, Vietnam

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 33 (2006): L19403, doi:10.1029/2006GL027772.Current models of drainage evolution suggest that the non-dendritic patterns seen in rivers in SE Asia reflect progressive capture of headwaters away from the Red River during and as a result of surface uplift of Eastern Asia. Mass balancing of eroded and deposited rock volumes demonstrates that the Red River catchment must have been much larger in the past. In addition, the Nd isotope composition of sediments from the Hanoi Basin, Vietnam, interpreted as paleo-Red River sediments, shows rapid change during the Oligocene, before ∼24 Ma. We interpret this change to reflect large-scale drainage capture away from the Red River, possibly involving loss of the middle Yangtze River. Reorganization was triggered by regional tilting of the region towards the east. This study constrains initial surface uplift in eastern Tibet and southwestern China to be no later than 24 Ma, well before major surface uplift and gorge incision after 13 Ma

Two-phase exhumation along major shear zones in the SE Tibetan Plateau in the late Cenozoic

Three continent-scale shear zones are arguably the most outstanding structural features in the southeastern Tibetan Plateau, and therefore, their tectonic and landscape evolution have significant implications for understanding the history and mechanisms of intracontinental mountain building and plateau growth. This study presents low-temperature thermochronology from the Gaoligong and Chongshan shear zones (GLSZ and CSSZ) and quantitative analyses of fluvial longitudinal profiles of tributaries in the Salween drainage, which lies between the shear zones. Apatite and zircon (U-Th)/He data reveal a two-stage exhumation history for both shear zones: rapid and prominent cooling in the middle Miocene followed by a second, lower magnitude cooling event in the late Miocene to early Pliocene. Ductile transpressional shearing is inferred to have caused the first cooling, continuing until ~11\ua0Ma. The northward migration of the tectonic events along the Mogok metamorphic belt and GLSZ and synchronous dextral displacement along the Jiali fault indicate the dominant role of the north advancing eastern Himalayan syntaxis on the surrounding structures. Increased river incision is identified in the middle Salween drainage, leading to two-segment river profiles and further exhumation along the GLSZ and CSSZ. The tributary transient response could result from temporal changes in uplift or adjustments of the trunk channel to climatic change. Furthermore, glaciers play an important role in shaping the landscape of the upper reaches of catchments in the northern segment of the shear zones. Different drivers for the two exhumation events may reflect distinct stages of plateau growth characterized by different crustal deformation patterns